Question

Chứng minh đẳng thức

\(\left(a+b\right)^2-\left(a-b\right)\left(a+b\right)=2b\left(a+b\right)\)

Answer 1

VT= (a+b)(a+b-a+b)

= (a+b)2b =VP => đpcm

Answer 2

\(VT=\left(a+b\right)^2-\left(a-b\right)\left(a+b\right)=a^2+2ab+b^2-a^2+b^2=2ab+2b^2=2b\left(a+b\right)=VP\)